It will only be use as payment system to increase the speed of transactions and when we are willing top adopt, we will have to surrender the benefits we are enjoying with the current no banking system which is we are only relying with exchange sites. Our accounts then will be audited from time to time and the risk of our accounts to be freeze will likely to happen.
The incoming banks for bitcoin themselves (if it's going to be realised) will automatically adapt to bitcoin and that bitcoin which they could control is what they have in their storage and it depends on the users who just moved their bitcoin to the banks.
It's right that the bank will be able to freeze or hold some accounts that are being suspicious and probably break their regulation upon user agreements as usually been asked in the first place, but the rest which outside of their coverage, I don't think so.